Motor vehicle brake



' G nl.. coTTER MOTOR VEHICLE BRAKE` Filed Feb. 17, v1954 Marh 24, 1936.

Patented Mar. 24, 1936 UNITED .STATI-:s

MOTOR VEHICLE BRAKE vGeorge L. Cotter, Wilkins'burg, Pa., assignor to The Westinghouse Air Brake Company, Wiln merdng, Pa., a corporation oi Pennsylvania Application February 17, 1934, Seria1 No.'711,693

v 6 Claims. (01488-181) A'I'his invention relates to motor vehicle brakes, and more specically to brakes for controlling the overspeed of vehicles.

When descending a grade inl a motor vehicle, it is usually necessary to apply the brakes in order to maintain a desired rate of speed. .Whether the approach to the grade is made at a high or a low speed, some degree of skill on the part of the operator must be exercised in applying thebrakes to prevent the -vehicle from reaching dangerous speeds. If during the descent the engine remains clutched to the driving shaft-it will pro- -duce an effective retarding` force, thereby requiring less force at the brakes. If, however, the vehicle is equipped with a so-called free wheeling device, or some other similar overspeed device, the retarding eiect of the engine may not be present, and the brakes must be applied with a greater force.

It is usually desirable that the speed of approach to a grade be maintained during the descent of the grade, and if this could be accomplished without requiring some skill on the part of the operator, it would greatly add to the comfort and ease of driving. With this in mind,

I contemplate as one object of my invention, the

provisionof a motor vehicle brake which acts automatically to prevent overspeeds in excess of that desired, as determined by manual operation of the throttle.

Another object of my invention is to provide a motor vehicle brake in which the braking'effect producedis proportional to the overspeed of the vehicle.

Ayet further object is to provide a vehicle brake of this character which is adaptable not only to the braking of overspeeds of a motor vehicle, but

Figure-3 is a similar view alongk the line of the same device. Y

Referring now to the drawing, I have provided an electro-dynamic brake device I0 of the eddy current type, associated with a drive shaft I2 of an automobile, a rheostat device I4 anda centrifuge' device I6, for controlling operation of the brake device, and a throttle mechanism I8 having means associated therewith for'controlling operation oi the rheostat device. i

'Ihe brake device I0 maybe of any of the 5 usual electro-dynamictypes, and I have, as one exampleindicated a simple' form of the eddy current type comprising a rotor 2`0"and a stator .The rotor 20 is preferably an annulus of some 10 magnetic material, such, fo'r example, as ironor steel, secured to the automobile drive shaft I2, as .by a. key- 24. The stator 22 is4 shown diagrammatically as comprising insulated windings i arranged to form magnetic poles adjacent the pe- 15 riphery of the rotor. f

It is to be understood, however, that instead ofthe simple form diagrammatically shown I-may use an eddy current brake in which the stator is provided with any desirednumber of project- 20 ing poles on which are disposed exciting windings; and, if desired,arotor having either a squir- `rel cage type of winding, or an insulated winding disposed thereon.

` The rheostat device I4 is provided with a mov- 25 able arm 26, .which is lpivo'tally' mounted at 28 and adapted to be moved into successive engagement with contacts 30 betweenwhich are connected segments of a resistance unit 32. The arm 26 is held in an"oi position, out ofv engage- 30 ment with the contacts 30, by a spring 341against astop33. f

When the movable arm 26 is moved into engagement with the contacts 3 0, the stator Winding of the eddy current brake device I0' is yener 35 gized from a source of current supply, such `for example, as a battery 35. The degree of energization depends upon the amount of the resistance unit 32 connected in the circuit. A switch 31 4may.4

bevprovided in the circuit for disconnecting the 40 battery at any desired time, independently of` operation of the movable arm 26. l

The movable arm 26 is adapted to be operated `by the centrifuge devicek I6. 'I'he centrifuge device is provided with two collar members 38 and 45 `38. The collar 38 is rigidly secured to the drive shaft I2, as by a key 40. The collar member 36'is .axially slidable on the drive shaft I2,and is connected to the relatively stationary collar 38 by resilient and flexible members 42. f 50 Intermediate the ends of these flexible mempbers"42 are secured weights or bodies 44. When the drive shaft I2 is rotated,` the centrifugal force due to rotation of the 44 "will'cause the v collar 36 to be slid axially to the right, and this 65 movement .will be transmitted to the movable arm 26 through a connecting rod 46.

The connecting rod 46 has one end thereof secured to the movable arm at 48, and the other end thereof provided with a forked portion 50 interfitting with a slot 52 in the slidable collar 36.

The centrifuge device is intended to operate the movable arm 26 for overspeedsof the vehicle only. To prevent 'the arm from being operated at other times I have provided a mechanism which is operable from the throttle mechanism I8. The rheostat device I4 is provided with a base member 54 having beveled edges 56 providing for'support of thebase member ina coacting slot or re- I W'hen the latch 64 is out of engagement with the teeth 62, the base member 54 isslidable in the supporting structure 6B. When the latch 64 isin engagement withv the teeth 62, the base member 54 may be moved to the left. in the supporting structure 60, but the vertical edges of the teeth 62 preventv movement to the right.v

For operating the latch 64 intoA and vout of engagement with the teeth 62, I have provided a link mechanism comprising bell crank levers 61, connecting rod 68, andlink 18. This mechanism is adapted to be actuated by a throttle foot pedal 12, through a link member 14. i

When the foot pedal 12 is depressed the latch 64 is disengaged from the teeth 62, but so long as the foot pedal is-in its uppermost position the latch 64 remains in engagement with the teeth. A spring 16 acts uponapin 18, which may be associated with the carburetor or other fuel regulating device, to position the foot pedal in its uppermost position.

In operation, the operator depresses the foot pedal 12 to effect ya supply of fuel to the engine,

in accordance with the rate of speed desired. This downward movement of the footpedal causes the latch 64 to be disengaged from the teeth 62.

As the vehicle accelerates, the centrifugalforce due to rotation of the bodies 44 about the shaft I2, will cause the collar 36`to move to the right. This movement of the collar will exert a pull on the rheostat arm 26. With the latch 64 disengaged from the teeth 62, the spring 34 is of sufllcient strength to hold the arm 26 against its stop 33, so that the result of this pull on the arm 26 is to move the entire rheostat device I4 to the right, it sliding in the recessed trackway 58 of the supporting structure 60, instead of merely moving arm 26 away from stop 33 and over the Y contacts 30. y

With the whole rheostat device moved to the right, the rheostatarm 26 is thus held out of engagement with the contacts 43l), so that the stator winding of the brake device I is as yet not energized. The rheostat device I4 will then be leased. 'Ihe rheostat device is then locked in position against further movement to the right, but due to the slope of the teeth 62 may be moved to the left.

As the vehicle descends the grade it will tend to overspeed, and as it does so thefbodies 44 will move further outwardly, causing the collar 36 to exert a greater pull on the rheostat arm 26. Since the rheostat base member 54 is locked against further movement to the right, this pull will move the rheostat'arm into engagement with'the contacts 3S, whereupon the stator winding of the brake device will be energized.

When current flows in the stator winding, a f

magnetic flux is produced which enters the rotor 28. Since the rotor 20 is rotating with movement of .the vehicle, eddy currents will be generated therein and these currents will in turn produce'a magneticilux counter to that produced by the stator winding, with the result that a retarding or braking force will be produced. This retarding force acts to prevent the vehicle from accelerating while descending the grade.

In case the initial retarding force due tov energization of the brake is insuicient to prevent acceleration, any increase in speed of the ve.

`hicle will cause a further movement of Itherheostat arm 26 to the right, whereupon resistance will be out outcf circuit and a. greater current will flow in the brake stator winding. The retarding force produced bythe brake device is ment will first return the rheostat arm 26 to its`V off position, and further movement will move the entire .rheostat device toward its no speed position. f

VIt-Will'be seen, therefore, that this arrangementwill not interfere with drifting of the car unless there is a tendency to pick up speed, at which time the apparatus functions to prevent the speed from increasing. 'Ihe limit of the speed is established at the time the foot pedal is permitted to assume its o ff position. Any slowing down of the car after that time `,automatically reduces the speed limit, which can be raised only by again depressing the foot pedal.

If at any time after releasing pressure `on the foot pedal it is desired to permit the. car to drift to overspeeds, the switch 31 may be opened, whereupon the brake is entirely ineffective.

While onev illustrative embodiment of the invention has been described in detail, it is not my intention to limit its scope to that embodiment or'otherwise than by the terms ofthe appended claims. v

Having now described my invenion, what I claim as new and desire to secure by Letters Patent,is:m i A 1. Ina vehicle brake apparatus, in combination, an auxiliary brake device, control means for effectingY operation of said brake device, means operated according to the, speed ,of the Y vehicle for vactuating said control means, a control element having a biased position and operable to other positions to effect a. speed of the vehicle according toi the degree of movement thereof, and meansv for Vpreventing said speed controlled means from actuating said control means whenv said element is in said other positions but permitting said speed controlled means to actuate said control means when said element is in said biased position.

2. In a vehicle brake apparatus, in combination, an electric brake device, a source of current supply, a circuit for connecting said source to said brake device, a circuit controller device having normally open contacts in said circuit, a centrifuge device for closing said contacts, a control element having idle and active positions, vand means for preventing said centrifuge device from effecting closing of said contacts when said control element is in an active position but operable to permit closing of said contacts by said centrifuge device when said element is in said idle position.

3. In a vehicle brake apparatus, in combination, an electric brake device, a stationary member, a movable member carried by said stationary member and movable with respect thereto, normally open contacts carried by said movable member, a control element having an idle position and an active position, locking means for locking said stationary and movable members against relative movement in a certain direction, a centrifuge device operable to close said contacts when said members are locked, and means for unlocking said members when said element is in said active position to prevent closing of said contacts by said centrifuge device.

4. In a vehicle brake apparatus, in combination, an auxiliary brake device, a control element having an idle position and movable to different operative positions to effect a speed of the vehicle in accordance with the degree of movement thereof, means for preventing operation of said brake device when said control element is in any operative position, and means rendered operative upon movement of said control element to said idle position for effecting operation of said brake device to a degree corresponding to the overspeed of the vehicle above that effected by movement of said control element to operative position.

5. In a vehicle brake apparatus, in combination`, an electric brake device, a source of current, a circuit for connecting said brake device to said source, a rheostat device for controlling the degree of current supplied to said brake device, a control element having an idle position and movable to an operating position to effect propulsion of the vehicle at a chosen speed, centrifuge means for operating said rheostat to effect a, supply of current to said brake device in accordance with the overspeed of said vehicle above said chosen speed, and means for preventing operation of said rheostat by said centrifuge means until said control element is returned to said idle position.

6. In a vehicle brake apparatus, in combination, an electric brake device, a pair of members providing for relative movement therebetween, means for effecting operation of said brake device to a degree according to the degree of relative movement between said members, means operated according to the speed of the vehicle for moving one of said members, a control device having an idle position and an operating position, and means for preventing relative movement of said members when said control element is in said active position but permitting relative movement when said control element is in said idle position.

GEORGE L. COTTER. 

